This invention relates to air jets for treating textile yarns, in particular for texturing multifilament yarns by subjecting the filaments to a turbulent airflow to increase the bulk of the yarns.
There are many such air texturing jets of differing designs currently in use, but they tend to fall within two basic types. The first type is an extrapolation of current interlacing jet technology, and consists of a tube through the bore of which the yarn to be textured is fed to be impinged upon by an air jet which enters the bore laterally through a side inlet. The air inlet may be angled to the longitudinal axis of the tube so that the incoming jet of air gives the yarn a forwarding impetus as well as bulking the yarn. Such a jet has good performance on low denier, singles and low overfeed yarn. The simple jet tube is tolerance sensitive to manufacture and has limited overfeed potential. The second type is a xe2x80x9cneedlexe2x80x9d jet, comprising a venturi tube through which the yarn to be textured is fed, and a xe2x80x9cneedlexe2x80x9d which is located axially in the xe2x80x9cmouthxe2x80x9d of the venturi tube to create an annular inlet for the a turbulent flow of air to enter the venturi. This second type performs better than the first type, particularly on heavier denier and high overfeed yarns. However, such a jet is more difficult to manufacture than the first type, and is extremely tolerance sensitive, since small differences in dimensions and setting create substantial air velocity differences and hence substantial variations in bulk levels imparted to the yarn. The flow of air into the venturi tube, and hence the degree of bulking of the yarn, is controlled by the annular restriction between the needle and the mouth of the venturi tube, a restriction which is very sensitive to the tolerances of manufacture of the needle and venturi tube and their relative positioning. In consequence the second type of air jet is very difficult to control in an attempt to obtain texturing consistency from position to position on a single machine or from machine to machine, and delicate adjustment is required to achieve optimum performance for a given type of yarn.
It is an object of the present invention to provide a yarn treatment jet of the second type, but with good control and with no or with minimum problems of manufacturing tolerance sensitivity. It is also an object of the present invention to provide an air jet which achieves the highest air velocities consistently with consistent high levels of turbulence to create maximum yarn tension. It is a further object to provide added flexibility of air jet construction for direct control of the air turbulence and for special yarn effects.
The invention provides an yarn treatment jet comprising a venturi member having a venturi shaped bore therethrough and extending downstream of a mouth of the bore, and an inlet member having a yarn passage therethrough and located in the mouth of the bore, wherein the inlet member is in contact with the mouth of the bore to locate the inlet member relative to the venturi member and is configured to provide a passage for air into the venturi bore between the inlet member and the venturi member.
Preferably the yarn passage in the inlet member is axially aligned with the venturi bore. The inlet member may comprise a core and a needle in mutual relatively locating contact, and the needle may have a yarn passage axially aligned with a yarn passage in the core. The air passage may comprise at least one groove in the outer surface of the inlet member and extending in the axial direction thereof. Alternatively, the air passage may be formed as at least one non-axial bore through the inlet member. The grooves or non-axial bores may be disposed in a circumferentially symmetrical arrangement, and may communicate with an annular chamber disposed between the inlet member and the venturi member. The annular chamber may have an axial length of up to 5 mm, and may be substantially 3.5 mm in length.